
const dataURLtoFile = (data, name) => {
  const arr = data.split(',')
  const mime = arr[0].match(/:(.*?);/)[1]
  const bstr = atob(arr[1])
  let n = bstr.length
  const u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new File([u8arr], name, {
    type: mime
  })
}


const compress = (img) => {
  const canvas = document.createElement('canvas')
  const ctx = canvas.getContext('2d')
  // 瓦片canvas
  const tCanvas = document.createElement('canvas')
  const tctx = tCanvas.getContext('2d')
  // let initSize = img.src.length;
  let width = img.width
  let height = img.height
  // 如果图片大于四百万像素，计算压缩比并将大小压至400万以下
  let ratio
  if ((ratio = (width * height) / 4000000) > 1) {
    // console.log("大于400万像素");
    ratio = Math.sqrt(ratio)
    width /= ratio
    height /= ratio
  } else {
    ratio = 1
  }
  canvas.width = width
  canvas.height = height
  //    铺底色
  ctx.fillStyle = '#fff'
  ctx.fillRect(0, 0, canvas.width, canvas.height)
  // 如果图片像素大于100万则使用瓦片绘制
  let count
  if ((count = (width * height) / 1000000) > 1) {
    // console.log("超过100W像素");
    count = ~~(Math.sqrt(count) + 1) // 计算要分成多少块瓦片
    //      计算每块瓦片的宽和高
    const nw = ~~(width / count)
    const nh = ~~(height / count)
    tCanvas.width = nw
    tCanvas.height = nh
    for (let i = 0; i < count; i++) {
      for (let j = 0; j < count; j++) {
        tctx.drawImage(
          img,
          i * nw * ratio,
          j * nh * ratio,
          nw * ratio,
          nh * ratio,
          0,
          0,
          nw,
          nh
        )
        ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh)
      }
    }
  } else {
    ctx.drawImage(img, 0, 0, width, height)
  }

  // 进行最小压缩
  const ndata = canvas.toDataURL('image/jpeg', 0.2)
  tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0
  return ndata
}



export const imgPreview = (file, e) => {
  const self = this
  // 看支持不支持FileReader
  if (!file || !window.FileReader) return
  return new Promise((resolve, reject) => {
    if (/^image/.test(file.type)) {
      // 创建一个reader
      const reader = new FileReader()
      // 将图片2将转成 base64 格式
      reader.readAsDataURL(file)
      // 读取成功后的回调
      reader.onloadend = function () {
        const result = this.result
        const img = new Image()
        img.src = result
        // 判断图片是否大于500K,是就直接上传，反之压缩图片
        if (this.result.length <= 500 * 1024) {
          const signImg = dataURLtoFile(this.result, file.name)
          resolve(signImg)
        } else {
          img.onload = function () {
            const data = compress(img)
            const signImg = dataURLtoFile(data, file.name)
            resolve(signImg)
          } 
        }
      }
    }
  })
}


/**
 * 环境判断
 */
function getCurrentPlatform() {
	let platform = '';
	//#ifdef APP-PLUS
	platform = 'APP-PLUS'
	//#endif

	//#ifdef APP-PLUS-NVUE
	platform = 'APP-PLUS-NVUE'
	//#endif

	//#ifdef H5
	platform = 'H5'
	//#endif

	//#ifdef MP-WEIXIN
	platform = 'MP-WEIXIN'
	//#endif
	return platform;
}

export const platForm = getCurrentPlatform();

